Agitator assembly for mixing paint

ABSTRACT

A paint agitator assembly comprising an impeller carried by a magnet in the cup for mixing the paint, with the pain discharge tube located between the impeller end and the cup wall for preventing a vortex. The magnet is rotated by a second magnet external to the cup, and the second magnet is in turn rotated by a high speed air turbine through a series of plastic gears arranged to provide speed reduction and high torque for rotating the first magnet. The air for driving the turbine is provided through a throttling valve and metering orifice to the air turbine and follows a tortuous path extending in sequence through circumferentially offset holes to reduce noise.

United States Patent Brehmer et al. Feb. 4, 1975 AGITATOR ASSEMBLY FORMIXING 2,655,011 10/1953 lhle 259/D1G. 46 PAINT 2,712,926 7/1955 Von259/108 3,672,645 6/1972 Terrels 259/122 [75] Inventors: John Brehmer,Cary; Russell C.

gz g f i ggggi gfi fi UL Primary Examiner-Robert W. Jenkins [73]Ass1gnee: gtfiiwzggtvllflrner Corporation, [57] ABSTRACT I A paintagitator assembly comprising an impeller car- [22] Flled' 1974 ried by amagnet in the cup for mixing the paint, with [21] App]. No.: 432,556 thepain discharge tube located between the impeller end and the cup wallfor preventing a vortex. The magnet is rotated by a second magnetexternal to the 259/108, 25%/(l))1ItG7./:g cup, and the Second magnet isin turn rotated by a I o n q s u 1 1 a e u u a u 1 s I I r s a [58] gfgz f'dg i'i" 35 2 432? 22 arranged to provide speed reduction and hightorque for rotating the first magnet. The air for driving the turbine isprovided through a throttling valve and me- 56 R f d tering orifice tothe air turbine and follows a tortuous 1 e erences path extending insequence through circumferentially UNITED STATES PATENTS offset holes toreduce noise.

1,784,416 12/1930 Brockmann 259/122 2,072,082 3/1937 Butts 259/122 14Clalms, 9 Drawmg Figures PATENTEB FEB 4191s SHEET 3 UF 3 AGITATORASSEMBLY FOR MIXING PAINT BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates in general to paint mixing and moreparticularly to an improved agitator assembly for mixing paint.

2. Description of the Prior Art Agitator assemblies for material mixingoften utilize a rotating magnet and impeller in a mixing vessel. Themagnet is rotated by a magnetic field usually provided by an externallylocated magnet, which is coupled to a power source. Magnetic couplinghas the advantage of avoiding a rotary seal in the vessel wall, which isrequired if the impeller is mechanically coupled to the power source.Such seals become clogged, especially when used with paint of the typeemployed inpainting auto bodies. Alternatively, providing sufficienttorque to rotate a magnet and impeller through magnetic coupling has notbe practical if the material is paint.

Thus, auto body paint utilizes heavy pigments or metal flakes or,alternatively, extremely light solvents so that the flake or pigmentsettles quickly. This situation in turn requires a relatively highmagnetic force or torque on the impeller to prevent pigment settling. Ifthe pigment settles during painting of the body or between successivepaint coats, the finished appearance is marred or uneven.

Various mixing approaches have been tried including a so-called triggerpaddle, balls in the cups, top and side mounted quasi displacement pumpsand air mixing. The trigger paddle is operated each time the operatoroperates the spray gun trigger and, therefore, does not stir oftenenough to mix the paint. Likewise, dumping balls in the cup, which movein response to occasional manual swirling of the cup, does not mix thepaint often enough to secure a good mix. The top and side mounted quasipumps directly drive propeller shafts in the paint and, therefore,require rotary seals which clog with paint and also result in variablespeed. These quasi pumps are similar to turbines but have close fittingchambers which are expensive. Air mixing in which air is blown throughthe paint-evaporates the solvent too rapidly and creates an undesirablefroth.

Using a true air driven turbine for rotating an external magnet toprovide a magnetic field for rotating a magnet and impeller in the paintcup would offer the most advantageous solution. However, the turbineoperates at high speeds and low torque. With low torque, the impellerstalls due to heavy pigments or flakes and good mixing does not occur.On the other hand, a positive displacement air motor of the vane or geartype to provide sufficient torque for rotating the magnets is relativelyexpensive. An air motor arrangement is also heavy and tiring to theoperator, since the cup and agitator assembly are usually manually held.Therefore, the use of a magnetically driven impeller to mix paintshaving heavy pigments or metal flakes has heretofore been subject to anumber of drawbacks.

SUMMARY OF THE INVENTION The present invention proposes to solve theabove and other problems in paint mixing apparatus by utilizing anagitator assembly having a low cost air turbine in conjunction with aspeed reduction gear train to rotate the magnets. With a low coatplastic turbine and plastic gears, this agitator assembly provides boththe LII proper speed and torque for mixing paint having heavy pigmentsor metal flakes, together with the requisite economy. The plasticturbine and gears are carried in a plastic housing to also minimizeweight and avoid tiring of the painters arm.

In order to provide maximum agitation of the paint while minimizingundesirable, vortex action, the paint discharge tube, which extends froman axial outlet conduit at one end of the paint cup, is extended'to aposition between the periphery of the impeller and the wall of the cup.

The air for driving the turbine is passed from a throttling valvethrough a metering orifice for application to the turbine and then ispassed sequentially through a series of circumferentially offset holesfor muffling noise and vibration. In addition, the turbine blades arespaced circumferentially at unequal positions to thereby avoid resonantnoises. The metering orifice provides a high speed air jet for theturbine, while limiting the applied air to thereby limit the drain onthe air supply compressor, which is important in preserving the airsupply, especially in the case of a low capacity compressor. The quasipumps mentioned previously allow large quantities of air to escape pastthe ends and sides of the blades and gears resulting in relativelyinefficient operation.

The paint impeller is also provided with a selfcentering arrangementwhich is effective to seat the impeller on its drive capstan in responseto jiggling the can in the event the impeller has been dislodged duringassembly of the cup lid and discharge tube.

It is therefore a primary object of the present invention to provide animproved economical agitator assembly for mixing paint.

Other objects and features of the present invention will become apparenton examination of the following specification, claims and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of aspray gun, together with an associated paint cup and agitator assemblyto which the principles of the present invention are applied;

FIG. 2 is a sectional view taken generally along the line 22 in FIG. 1;

FIG. 3 is a sectional view of the paint cup and agitator assembly takengenerally along the line 3-3 in FIG. 2;

FIG. 4 is a sectional view of the paint cup taken generally along theline 4-4 in FIG. 3;

FIG. 5 is a sectional view taken generally along the line 5-5 in FIG. 3;

FIG. 6 is a sectional view taken generally along the line 66 in FIG. 3;

FIG. 7 is a sectional view taken generally along the line 7-7 in FIG. 3;

FIG. 8 is a sectional view taken along the line 88 in FIG. 7; and

FIG. 9 is a sectional view taken along the line 9-9 in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I a conventional spraygun I0 is shown carrying a paint cup 12 connected thereto by means of aconventional conduit and fitting assembly 14. Assembly 14 may, forexample, be of the type such as shown in US. Pat. No. 3,714,967 issuedFeb. 6, 1973 to Zupan et al. The spray gun is fed air by means of aconventional hose assembly 16 connected to a conventional pressurizedair supply or compressor (not shown), which supplies air usually in arange between 40 psi. to 75 p.s.i., for the purpose of siphoning paintfrom the paint cup assembly 12 through the conduit and fitting assembly14 for dispersion through a nozzle assembly 18 of the spray gun.Alternatively, the pressurized air is applied to the paint through aconduit (not shown) to drive it under pressure through the assembly l4and gun 10. The paint from the nozzle assembly 18 is directed toward anobject to be painted by an operator, whose hand holds the gun l0 and cup12 by means of handle 20 on the gun.

The paint cup 12 carries an agitator assembly 24 for mixing paint in thecup. A flexible conduit 26, connected to the air supply through athrottling valve 28 in the hose assembly, supplies air to the agitatorassembly 24. The valve 28 permits air to be optionally supplied at aselected rate to assembly 24.

The paint cup 12 includes a back wall 30 and a peripheral wall 32 havingan open end, which is closed by a lid 34, as seen in FIGS. 2 and 3.

The lid 34 has an annular gasket 36 seated in a recess adjacent the lidperiphery for engaging the open end of cup 12 under pressure of athreaded sleeve 38. The sleeve 38 encircles a conduit 40 passing axiallythrough the lid 34 into the cup 12 through an appropriate orconventional seal. The threaded portion of sleeve 38 engages a threadedopening in the back leg of a U- shaped locking bracket 42 having slotsin the end legs thereof for engagement with a pair oflugs 44 projectingradially outwardly from adjacent the upper end of wall 32.

The sleeve 38 is manually threaded through the back wall of lockingbracket 42 by means of handle 46 to lift the bracket against lugs 44 andbear against the lid 34 to secure the lid or cover tightly against theopen end of wall 32. Conduit 40 has a fitting 48 at one end projectingfrom lid 34 for attachment to the spray gun 10. The outer end of theconduit 40 projecting into the cup 12 sealingly communicates with oneend of an aluminum paint discharge tube 50.

The tube 50 projects downwardly and radially outwardly to a positionadjacent the juncture of the cup back wall 30 and peripheral wall 32 andradially outwardly of the ends of an impeller or vane 52 of the agitatorassembly 24, as seen in FIGS. 3 and 4.

The impeller 52 comprises a longitudinally or radially extending vaneintegrally formed on a plastic cup member 54. An apertured axial fingergrip or projection 56 is formed intermediate the ends of impeller 52.The cup member 54 is moulded around a magnet 58 having an annular steelback plate 60 secured to the upper surface of magnet 58 and adjacent thecup back wall. The cup 54, magnet 58 and impeller 52 are rotatablysupported by a capstan 62 in a position spaced from wall 30.

The capstan 62 has a beveled or conical periphery with the smalldiameter at one axial upper end for seating against the back wall of thecup member 54. An integrally formed threaded projection 64 is formed atthe lower or other capstan end extending axially through the back wall30 of the paint cup 12. A steel shaft 66 substantially one inch long andhaving threaded axial openings at opposite ends, threads onto projection64 and tightly seals the bottom capstan surface against the back wall30. The opposite lower threaded axial end of shaft 66 is engaged by'ascrew 58 for securing a cupshaped housing 70 to the shaft 66 and cup 12.

The housing 70 comprises a pair of radially spaced circumferential walls72 and 74 whose upper axial ends bear against the lower surface of aradial wall 76. The upper surface of wall 76 bears against a top annularwall or section 78 overlappingly engaging the surface of cup wall 32. Aradially inwardly extending wall80 is formed integrally on wall 78 forengagement with the cup back wall 30. Screws 82, passing through theback wall of housing 78 between walls 72 and 74 through wall 76, arethreaded into locating lugs 84 formed on walls 78 and 80, and serve tosecure walls 76 and 78 to housing 70 and in turn to shaft 66 and cup 12.

The shaft 66 also carries an axially extending bushing or bearing member86 for rotatably supporting a plastic turbine 88, seen in plan view inFIG. 7. A hub extending axially from turbine 88 has a small diametergear 90 integrally formed thereon. The turbine 88 has a plurality ofcircumferentially spaced radially extending teeth or vanes 92 to enablethe turbine 88 and gear 90 to be rotated or driven by the passage of airagainst the vanes. It will be noted that the turbine blades 92 arespaced circumferentially at unequal positions, in this case sixdifferently spaced positions, to minimize resonant noises with thenumber and location of the vanes being chosen to maintain the turbinebalance.

The turbine 88 is located axially between wall 76, the back wall ofhousing 70 and within wall 74, which forms a turbine chamber to whichair is supplied under pressure through a passageway 94 in a wall section96 formed between walls 72 and 74 at one circumferential position. Airis communicated to passageway 24, seen in FIGS. 7, 8 and 9, from theconduit 26 and an appropriate fitting tangentially into the turbinechamber through a reduced metering portion 98 of passageway 94 fordriving the turbine. Metering through orifice 98 provides a constantflow of high speed air. The air exits through a central opening formedin the radial wall 76 about gear 90, as seen best in FIG. 6, throughopenings 100 formed in wall 76 at positions spaced radially betweenwalls 72 and 74, and exits to atmosphere through openings or passageways102 formed in the back wall of housing 70. The openings 102 are offsetcircumferentially from passageways or openings 100 for the purpose ofmuffling or reducing the noise of air passing through the describedpath. Ribs 103 on wall 76 assist in stiffening wall 76 and reducing airnoise.

The gear 90 engages a larger diameter plastic gear 104 rotatably carriedon a bushing 106 and a coaxial pin 108 mounted at opposite ends inradial walls 76 and 80. A small diameter gear 110, axially displacedabove gear 104, is integrally formed on the hub of gear 104 and it inturn engages a large diameter plastic gear 112, as may be seen in FIG.5. The gear 112 is rotatably carried on the shaft 66 and has an annularprojection 114 thereon moulded around a magnet 116 to mouldably securethe gear and magnet, and a steel back plate 118 secured to the lowersurface of magnet 116. Magnet 116 is located adjacent, but spaced from,wall 30 and serves to rotate or drive the magnet 58 and impeller 52.Thrust washers or retaining rings are also provided for the gears andwheel, and the washers properly space the gears and wheels.

In assembling the agitator assembly 24 to the cup, the capstan stud orprojection 64 is inserted through the axial opening in wall 30, and theshaft 66 carrying housing 70 and walls 76 and 78, together with wheel 88and gears 90, 104, 110 and 112, are secured thereto. The impeller 152 isinserted into the cup 12 and the cup 54 engaged with the capstan 62. Itwill be noted that agitator assembly 24 may occupy any angular positionrelative wall 30.

Thereafter, paint is deposited in the cup 12 and the lid 34, togetherwith the conduit and fitting assembly 14, are placed in position withthe paint discharge tube 50 located between the radial end of vane orimpeller 52 and wall 32. If the impeller 52 is cocked relative thecapstan 62 when placing the tube 50 in position, the cup 12 is simplyjiggled or swiveled about a vertical axis to align the magnets 58 and116, which attract each other, to seat the cup 54 on capstan 62.

The fitting 48 is attached to the gun l0, and conduit 26 is connectedbetween passageway 94 and the throttling valve 28. Application of airpressure to the gun through hose assembly 16 creates a vacuum in thesiphon or paint discharge tube 50 so that paint is pressed through tube50, conduit 40 and through the gun nozzle 18 for dispersion to theobject to be painted. Atmospheric air is supplied to the cup 12 in aconventional manner through a small opening in lid 34. Alternatively,air under pressure is supplied to drive the paint through tube 50 underpressure.

Air is also supplied from conduit 26 through passageways 94 and 98 fortangentially engaging the turbine vanes 92 to rotate the turbine 88 andgear 90 at high speed of substantially 6,000 R.P.M. The unequal vanespacing prevents the buildup of resonance and minimizes noise. Gear 90and the remaining gears 104, 110 and 112 are arranged as speed reductiongears to provide a to 1 speed reduction so that magnet 116 is rotatedthrough the gear train relatively slowly at 400 R.P.M. and therebyprovides adequate torque to rotate magnet 58 against the heavy paintload. Magnet 58 carries cup 54 and impeller 52 into rotation to agitateand mix the paint. Movement of the paint would normally create a vortexand prevent adequate mixing, but tube 50 disrupts the vortex and drivesthe paint back over the vane 52 to ensure good mixing. The air, afterdriving the turbine 88, exits through the central opening in wall 76,through the openings 100 and 102 in wall 76 and the back wall of housing70, respectively.

It will be noted that the throttling valve 28 permits air to beselectively supplied to agitator assembly 24 in the proper amount, whenneeded for paint mixing, and to be terminated when unnecessary. Meteringorifice 98 serves to limit the air drain on the supply compressor tosubstantially 7f; c.f.m., while providing a high speed jet for drivingthe turbine. This ensures that sufficient air pressure is available todrive the paint through the gun 10 even if the compressor capacity is aslow as 5 c.f.m.

Various modifications of the described agitator assembly can beconstructed without departing from the concepts of the invention, whichare set forth in the accompanying claims.

What is claimed is:

1. An agitator assembly for a paint cup having a back wall and aperipheral wall, comprising a first magnet, an impeller, means securingsaid impeller to said first magnet, means on the back wall of said paintcup for rotatably supporting said first magnet and impeller in saidpaint cup, a second magnet, means supporting said second magnet forcoaxial rotation with said first magnet and external to said cup in aposition adjacent to said cup back wall for rotating said first magnetin response to rotation of said second magnet, an air turbine, aplurality of speed reduction gears, and means rotatably supporting saidgears and turbine with said gears interconnected between said turbineand said second magnet for rotating said second magnet at a speedsubstantially below the speed of said turbine in response to therotation of said turbine.

2. The assembly claimed in claim 1 in which said gears are formed ofplastic.

3. The assembly claimed in claim 2 in which said means for securing saidimpeller to said magnet comprises a cup member formed of plastic havinga peripheral wall in encircling engagement with said magnet, and saidimpeller is integrally formed on said cup memher.

4. The assembly claimed in claim 3 in which said means on said paint cupcomprises a capstan formed of plastic having one end for rotatablysupporting said plastic cup member and first magnet, an axiallyextending wall passing axially through said first magnet, and aprojection at the other end of said capstan extending through said paintcup back wall.

5. The assembly claimed in claim 4 in which said means supporting saidgears comprises a shaft secured at one end to said capstan projection, apair of axially spaced radially extending walls encircling said shaft, a

cup-shaped plastic housing, means securing the back wall of saidcup-shaped plastic housing to the other end of said shaft with saidturbine and a first small diameter gear rotatably supported on saidshaft and located axially intermediate the back wall of said plastichousing and one of said radially extending walls, said second magnet anda large diameter gear rotatably supported on said shaft intermediatesaid radially extending walls, and an integrally formed large and smalldiameter gear rotatably supported between said radially extending wallsfor engaging said turbine small diameter gear and second magnet largediameter gear respectively.

6. In the assembly claimed in claim 1, a metering orifice for supplyingair under pressure at a limited rate and tangentially to said turbine.

7. In the assembly claimed in claim 6, valve means for selectivelysupplying pressurized air at a controlled rate to said metering orificeto drive said turbine.

8. In the assembly claimed in claim 1, a paint discharge tube for saidpaint cup with said discharge tube having a terminating portion locatedbetween said impeller and the peripheral wall of said paint cup andadjacent the back wall of said paint cup.

9. The agitator assembly claimed in claim 1 in which said turbineincludes vanes spaced at circumferentially unequally spaced positions.

10. An agitator assembly for a paint cup having a back wall and aperipheral wall, comprising a magnet, an impeller carried by saidmagnet, means extending through the back wall of said cup for rotatablysupporting said magnet and impeller in said cup, a second magnet, ashaft secured to said extending means, means including a large diametergear secured to said second magnet and supporting said second magnet forrotation about the axis of said shaft in a position axially aligned withsaid first magnet and adjacent to said back wall for rotating said firstmagnet in response to rotation of said second magnet, an air turbineincluding an integrally formed small diameter gear supported forrotation.

about the axis of said shaft at a position axially spaced from saidpaint cup back wall, and a pair of integrally formed gears rotatablysupported for engaging said turbine gear and said second magnet gearrespectively for rotating said second magnet at a speed substantiallybelow the speed of said turbine in response to the rotation of saidturbine.

11. In the assembly claimed in claim 10, a cupshaped housing secured tosaid shaft with a metering orifice therein for passing air underpressure in a direction tangential to the vanes of said turbine.

12. In the assembly claimed in claim 11, a throttling valveinterconnected between said orifice and a source of pressurized air forcontrolling the application of air to said metering orifice.

13. In the assembly claimed in claim 12, circumferentially offset airpassageways for sequentially passing air to atmosphere after passagetangential to said vanes to thereby limit the noise and vibrationcreated by said air.

[4. In the assembly claimed in claim 10. a lid for said paint cup, and apaint discharge tube secured to said lid at a position coaxial with saidshaft and extending to a position adjacent the path described by aradial end of said impeller.

1. An agitator assembly for a paint cup having a back wall and aperipheral wall, comprising a first magnet, an impeller, means securingsaid impeller to said first magnet, means on the back wall of said paintcup for rotatably supporting said first magnet and impeller in saidpaint cup, a second magnet, means supporting said second magnet forcoaxial rotation with said first magnet and external to said cup in aposition adjacent to said cup back wall for rotating said first magnetin response to rotation of said second magnet, an air turbine, aplurality of speed reduction gears, and means rotatably supporting saidgears and turbine with said gears interconnected between said turbineand said second magnet for rotating said second magnet at a speedsubstantially below the speed of said turbine in response to therotation of said turbine.
 2. The assembly claimed in claim 1 in whichsaid gears are formed of plastic.
 3. The assembly claimed in claim 2 inwhich said means for securing said impeller to said magnet comprises acup member formed of plastic having a peripheral wall in encirclingengagement with said magnet, and said impeller is integrally formed onsaid cup member.
 4. The assembly claimed in claim 3 in which said meanson said paint cup comprises a capstan formed of plastic having one endfor rotatably supporting said plastic cup member and first magnet, anaxially extending wall passing axially through said first magnet, and aprojection at the other end of said capstan extending through said paintcup back wall.
 5. The assembly claimed in claim 4 in which said meanssupporting said gears comprises a shaft secured at one end to saidcapstan projection, a pair of axially spaced radially extending wallsencircling said shaft, a cup-shaped plastic housing, means securing theback wall of said cup-shaped plastic housing to the other end of saidshaft with said turbine and a first small diameter gear rotatablysupported on said shaft and located axially intermediate the back wallof said plastic housing and one of said radially extending walls, sAidsecond magnet and a large diameter gear rotatably supported on saidshaft intermediate said radially extending walls, and an integrallyformed large and small diameter gear rotatably supported between saidradially extending walls for engaging said turbine small diameter gearand second magnet large diameter gear respectively.
 6. In the assemblyclaimed in claim 1, a metering orifice for supplying air under pressureat a limited rate and tangentially to said turbine.
 7. In the assemblyclaimed in claim 6, valve means for selectively supplying pressurizedair at a controlled rate to said metering orifice to drive said turbine.8. In the assembly claimed in claim 1, a paint discharge tube for saidpaint cup with said discharge tube having a terminating portion locatedbetween said impeller and the peripheral wall of said paint cup andadjacent the back wall of said paint cup.
 9. The agitator assemblyclaimed in claim 1 in which said turbine includes vanes spaced atcircumferentially unequally spaced positions.
 10. An agitator assemblyfor a paint cup having a back wall and a peripheral wall, comprising amagnet, an impeller carried by said magnet, means extending through theback wall of said cup for rotatably supporting said magnet and impellerin said cup, a second magnet, a shaft secured to said extending means,means including a large diameter gear secured to said second magnet andsupporting said second magnet for rotation about the axis of said shaftin a position axially aligned with said first magnet and adjacent tosaid back wall for rotating said first magnet in response to rotation ofsaid second magnet, an air turbine including an integrally formed smalldiameter gear supported for rotation about the axis of said shaft at aposition axially spaced from said paint cup back wall, and a pair ofintegrally formed gears rotatably supported for engaging said turbinegear and said second magnet gear respectively for rotating said secondmagnet at a speed substantially below the speed of said turbine inresponse to the rotation of said turbine.
 11. In the assembly claimed inclaim 10, a cup-shaped housing secured to said shaft with a meteringorifice therein for passing air under pressure in a direction tangentialto the vanes of said turbine.
 12. In the assembly claimed in claim 11, athrottling valve interconnected between said orifice and a source ofpressurized air for controlling the application of air to said meteringorifice.
 13. In the assembly claimed in claim 12, circumferentiallyoffset air passageways for sequentially passing air to atmosphere afterpassage tangential to said vanes to thereby limit the noise andvibration created by said air.
 14. In the assembly claimed in claim 10,a lid for said paint cup, and a paint discharge tube secured to said lidat a position coaxial with said shaft and extending to a positionadjacent the path described by a radial end of said impeller.